The present invention relates to a constant force generator mechanism, and to a continuously adjustable seat constructed with such mechanism.
Various types of hydraulic, pneumatic and electrical drive units have been designed for generating a constant force, but such devices are usually of expensive construction and therefore of very limited application. Several mechanical devices have also been developed for this purpose, such as counter-balancing weights and tensator springs, but as a rule, these mechanical devices, at best, are capable of generating a force which is nearly constant, and then only over a limited range of motion of the mechanism. Probably the closest approximation to a constant force generator mechanism so far achieved to date is that described in the publication Harmening, N. "Static Mass balancing with a Torsion Spring and Four-Bar Linkage," ASME Paper No. 74-DET-29, which mechanism includes a four bar linkage and torsion spring balancing mass statically, i.e. to generate a constant vertical force. However, even this mechanism is an approximation.
An object of the present invention is to provide a constant force generator mechanism based on an exact analytical solution to generate a constant force. Another object of the invention is to provide such a mechanism of simple construction so that it may be used as a basic mechanism or modular unit for inclusion in a large number of different applications. A still further object of the present invention is to provide, as one application of the basic mechanism, a chair having a seat continuously adjustable in height with respect to its frame by means of the novel constant force generator mechanism.